Mineral oils containing a graft polymer of natural rubber and polydiene



United States Patent 3,549,535 MINERAL OILS CONTAINING A GRAFT POLYMEROF NATURAL RUBBER AND POLYDIENE David W. Young, Homewood, and Richard F.Poss, Flossmoor, Ill., assiguors to Sinclair Research, Inc., New York,N.Y., a corporation of Delaware N0 Drawing. Original application June24, 1965, Ser. No. 466,822, now Patent No. 3,440,187, dated Apr. 22,1969. Divided and this application Mar. 27, 1969, Ser. No. 841,166

Int. Cl. Cm 1/28; C101 1/18 US. Cl. 25252 3 Claims ABSTRACT OF THEDISCLOSURE This application is a division of application Ser. No.466,822, filed June 24, 1965, now US. Pat. No. 3,440,- 187, issued Apr.22, 1969.

This invention relates to a novel graft polymer having utility as amineral oil pour point depressor. More specifically, the invention isdirected to a pour depressor which is a mineral oil-soluble, graftpolymer of natural pale crepe rubber and a certain liquid polydiene.

It is known in the art to add pour depressors to mineral oil bases inorder to permit their flow at low temperatures. Many different types ofmaterials depress the pour point of hydrocarbon oils, but most of theadditives have to be employed in disadvantageously large concentrationsto provide the desired results. Moreover, although use of certainpolymers as pour depressors is known, most hydrocarbon polymers, asdemonstrated by U.S. Pat. No. 3,048,479 to Ilnyckyj et al., are noteffective as pour point depressors and many in fact increase the pouroint.

p It has now been found that a base oil-soluble graft polymer of about 1to 20% by weight of a liquid polydiene to be described below, and about80 to 99% by weight natural pale crepe rubber, having a Staudingermolecular weight of about 25,000 to 200,000, when added to a basemineral oil in small, effective amounts, substantially reduces the pourpoint of the oil. Advantageously the graft polymer is of about 3 to 10%by weight, preferably 5 to 8% by weight, polybutadiene and about 90 to97% by weight, preferably 92 to 95% by weight, natural pale crepe rubberand the polymer has a Standinger molecular weight of about 35,000 to250,000. Preferably the rubber is relatively fresh, that is, not morethan about one year old as measured from the time the gutta percha isremoved from the natural rubber to give the crepe rubber.

The novel graft polymer of the present invention may be convenientlyobtained by compounding or intimately mixing the natural rubber on arubber mill at a temperature of about 100 to 250 F., preferably 150 to200 F., for about 5 to 30 minutes, preferably 8 to minutes, with thepolybutadiene oil. The mixture reacts on the mill to form the novelgraft polymer which shows improved properties in reducing the pour pointof base mineral oils. The reaction of the rubber and oil is e-videncedby a reduction in surface tack and an increase in molecular weight.

3,549,535 Patented Dec. 22, 1970 The polydiene oils used in thisinvention are normally liquid polymers generally having at least about1.8 allylic terminal hydroxyl groups per polymer molecule on theaverage. These hydroxyls are attached to terminal carbon atoms which inturn are primarily primary carbons. Most advantageously, the polydienepolymer has greater than two average terminal hydroxyl groups, e.g., atleast 2.1 to, say, 2.6 or even 3 or more. Also, two terminal hydroxylsare generally separated by a long carboncarbon chain. The polydienegraft-polymerized with rubher in the composition of this inventiondiffers from the homopolymers and copolymers of butadiene and relateddienes which are commercially available as GR-S rubbers, etc. The dienepolymer may have a viscosity at 30 C., of about 5-20,000 poises,preferably about 15 to 5000 poises. Often the polymer is obtained in aviscosity range of about 20 to 300 or 500 poises at 30 C. Preferredhomopolymers have a viscosity of about 35 to 60 poises or about 190 to260 poises at 30 C. Thus, the diene polymers are essentially liquids,including semisolids flowable under moderate pressure at ambienttemperatures in the range of F., to 400 R, which enables them to bereadily milled with the natural rubber. The hydroxyl-containing dienepolymers will have number average molecular weights in the range ofabout 400 to about 25,000 as determined by cryoscopic, ebullioscopic orosmometric methods. The preferred hydroxylcontaining diene polymers willbe in the molecular weight range of about 900 to 10,000. In contrast,conventional diene polymers such as GR-S rubber are extremely high inmolecular weight, e.g., in the range of several hundred thousand andare, therefore, rubberlike materials which are not useful for graftpolymerization with natural rubber. The latter diene olymers are toohigh in molecular weight to be worked at ambient temperatures and arenot reactive with natural rubber under normal milling conditions.

The diene polymers which are used in this invention have primaryhydroxyl groups which are allylic in configuration, thereby being of amore reactive nature in the graft polymerization reaction. The preferreddiene polymer also has the majority of its unsaturation in the mainhydrocarbon chain.

The dienes which are employed to make the first intermediate polymersare unsubstituted, 2-substituted or 2,3- disubstituted, 1,3-dienes of upto about 12 carbon atoms. The diene preferably has up to 6 carbon atomsand the substituents in the 2- and/or 3-position may be hydrogen, alkyl,generally lower alkyl, e.g., of 1-4 carbon atoms, aryl (substituted orunsubstituted), halogen, nitro, nitrile, etc. Typical dienes which maybe employed are 1,3-butadiene, isoprene, chloroprene,2'cyano-l,3-butadiene, 2,3-dimethyl-1,3-butadiene, etc. The dienes maybe polymerized along with alpha-olefin monomers, e.g., styrene, to givecopolymer materials suitable for use in this invention.

The choice of diene will usually depend upon properties desired in thefinal elastomer resin; for example, chloroprene may be used, alone or inadmixture with other dienes to produce oil-resistant and flame-proofrubbers.

The hydroxyl-terminated diene polymers used in accordance with thepresent invention preferably have a hydroXyl-functionality greater thantwo, e.g., in the range of 2.1 to 2.6, although the functionality mayexceed the range cited, e.g., it may range up to three or more. Thosepolymers of greatest utility have been found to have primary hydroxylgroups in terminal allylic positions on the main, generally longest,hydrocarbon chain of the molecule. By allylic configuration is meant thealpha-allylic grouping of allylic alcohol, that is, the hydroxyls of theintermediate polymer or the hydroxyl residues of the finished elastomerare attached to a carbon adjacent to a double-bond carbon.

The number and location of the hydroxyl groups and the molecular weightof the liquid polymer are for the most part a function of polymerizationtemperature and the type of addition polymerization system employed informing the polymer. It has been found that diene polymers of thedesired configuration may be obtained using hydrogen peroxide as thecatalyst for polymerization. This free-radical addition polymerizationusually takes place at a temperature of about 100 to 200 C., preferablyabout 100-150 C.

The reaction preferably takes place in a mutual solvent system; that is,one which dissolves both the diene monomer and the hydrogen peroxide.Suitable solvents are isopropanol, acetone, methanol, sec-butanol,n-butanol, npropanol and like alcohols having 2 to about 12 carbonatoms.

The H O -solvent system is found to supply hydroxyl groups and thecatalytic and solvent effects needed to produce the diene polymers ofdesired chemical and physical characteristics. In such a polymerizationsystem, the alcohol serves as a solvent for the peroxide and as asolvent or diluent for the diene monomer and is used in an amountsuitable to promote adequately rapid but controllable polymerization ofthe monomer material in the solution to form the diene polymers. Thealcohol will be free of any group which would interfere with theproduction of the desired diene polymer. Saturated alcohols arepreferred and often those having about the same carbon atom content asthe diene monomer will be found most useful. Thus, propanol orisopropanol is often used in butadiene polymerization. The H O -alcoholsystem may also contain ketones, ethers, alcohol-ketones, alcoholethersand alcohol-esters which are miscible in water in all proportions andwhich do not contain polymerizable carbon-to-carbon unsaturation orotherwise interfere with polymerization or enter into the product. Theperoxide material may be used in amounts of about 1% to 10% of thereaction mixture to assure a low molecular weight addition polymerproduct having more than about two hydroxyl groups per molecule.

The usable liquid (including semi-solid, etc.) polymers of butadienewill preferably conform to the following simplified chemical structure:

in which 11 plus p is greater than q, that is, the in-chain unsaturationaccounts for more than 50% of the unsaturation. One or more of the Hatoms appearing in the above formula will be replaced by hydroxyl in atleast some of the molecules. This formula should not be understood asimplying that the polymers are necessarily in blocks, but thecis-1,4-trans-1,4- and vinyl (1,2) unsaturation are usually distributedthroughout the polymer molecule. The letter 11 may be a numbersufficient to give a cis-l,4-unsaturation content of about -30 percent;p may be a number sufficient to give a trans-1,4-unsaturation content tothe polymer in the range of about 40-70 percent while q may besufficient to give a pendant 1,2- vinyl unsaturation of about 1035percent. Often the polymer will contain largely trans-1,4-units, e.g.,about 50-65 percent and about -25 percent cis-1,4-units, with about15-25 percent 1,2-units. Branching may also occur in the above polymers,especially those prepared at higher temperatures. It should beemphasized, however, that the present invention is not necessarilylimited to the use of hydroxyl-containing polydiolefins having thepredominating tras-1,4-structure, although such are highly preferred,where otherwise suitable polymers having high cis-1,4forms areavailable.

Among the mineral oil bases which are improved in accordance with thisinvention are normally liquid petroleum oils boiling primarily above thegasoline range and including, for instance, lubricating oils, dieselfuels, fuel oils, etc. These oils are often petroleum middle distillatesand commonly have relatively'high pour points, for in- Stance, at leastabout l0 F., or higher. The oils can be in their relatively crude state,or they can be treated in accordance with well-known commercial methodssuch as acid or caustic treatment, solvent refining, clay treatment,hydrotreating, etc. Fuel oils which can be improved by the graftpolymers of this invention are, for instance, hydrocarbon fractionsboiling primarily in the range of about 300 to 750 F. The fuel oils canbe straight run distillate fuel oils, catalytically or thermally crackeddistillate fuel oils or mixtures of straight run fuel oils, naphthas andthe like with cracked distillate stocks. The cracked materials willfrequently be about 15 to 70 volume percent of the fuel.

The amount of the graft polymer added to the base oils may be dependentupon the particular oil employed, but in all cases will be thatsufiicient to reduce the pour point significantly. Often the amountsused will fall in the range of about 0.01 to 2% or more by weight,preferably about 0.05 to 1.0% by weight, based on the mineral oil. Thecomposition may contain other ingredients such as other rubbers, carbonblack, sulfur, etc. The composition of the present invention may also beused as an oil extender for synthetic rubbers. The addition of thepresent composition to synthetic rubber such as styrene-butadienecopolymers, provides easier low temperature blending with about 5 to 35%mineral lubricating oil to give products of better low temperaturehysterisis properties.

The following examples are included to further illustrate the presentinvention.

EXAMPLE I To a glass bottle containing 3 ml. of aqueous 50% by weighthydrogen peroxide was added 30 ml. of tertiary butanol and grams ofbutadiene-1,3. The bottle was capped and placed in a steam pressurechamber and held at C., for 2 hours. After cooling, the bottles wereopened, and, from the polybutadiene therein, the volatiles were removed,e.g. butadiene-1,3, butadiene dimer, tertiary butanol, acetone, residualhydrogen peroxide, water, etc. This removal was accomplished with theaid of heat and vacuum, followed by steam and vacuum. The resultingproduct was 48 grams of clear, colorless, viscous liquid polybutadiene,having a molecular weight of about 1900 and a viscosity of about 220poises.

EXAMPLE II 46.25 grams of pale, yellow natural crepe rubber, having amolecular weight of about 75,000 is compounded on a rubber mill with3.75 grams of polybutadiene oil having a molecular weight of about 1900,a viscosity of about 220 poises and a hydroxyl number of about 0.802 andmade by using an aqueous H O -mutual solvent polymerization medium, at atemperature of F., for 10 minutes. An oil-soluble graft polymer resultsin an almost 100% yield. The polymer in an amount of 0.5% by weight isblended with a No. 2 petroleum fuel oil and the pour point (ASTM methodD9747) is determined. The No. 2 fuel oil is a blend of 50% straight rungas oil and 50% catalytically cracked gas oil which No. 2 fuel has apour point of 0 to 5 F. The pour point of the graft polymercontainingNo. 2 fuel oil is 40 F.

The following table shows the results of adding to the No. 2 fuel oil(1) only natural pale crepe rubber (2) the product of natural pale creperubber milled with 3% of the polybutadiene oil having a molecular weightof about 1900, a viscosity of about 220 poises and a hydroxyl number ofabout 0.802 and made by using an aqueous H 0 mutual solventpolymerization medium (3) natural pale crepe rubber milled with 7.5% ofpolybutadiene oil having a molecular weight of about 1900, a viscosityof about 220 poises and a hydroxyl number of about 0.802 and made byusing an aqueous H O -mutual solvent polymerization medium and (4)natural pale crepe rubber milled with 10.0% of polybutadiene oil havinga molecular weight of about 1900, a viscosity of about 220 poises and ahydroxyl number of about 0.802 and made by using an aqueous H O -mutualsolvent polymerization medium. Milling was accomplished as noted above.

TABLE I Percent by weight Percent Pour poly- Amount point, butadieneadded F.

From the table, it can be seen that a reduction in pour point superiorto that afforded by the rubber alone is attained by adding the graftpolymer to the fuel oil. Also, it is shown that the results obtained bymilling only 7.5% polybutadiene with the natural rubber were superior tothose obtained by milling 10% polybutadiene with the rubber.

It is claimed:

1. A liquid mineral oil boiling primarily above the gasoline rangecontaining a small amount, sufiicient to provide the said oil with areduced pour point, of a mineral oil-soluble, polymer having aStaudinger molecular weight of about 35,000 to 250,000, said polymerbeing the graft polymerization product of about to 99% by weight ofnatural, pale crepe rubber and about 1 to 20% by Weight of a polydienepolymer having an average of at least about 1.8 hydroxyl groups permolecule, a viscosity at 30 C. of about 5 to 20,000 poises and a numberaverage molecular weight of about 400 to 25,000, said diene being a1,3-diene hydrocarbon of 4 to about 12 carbon atoms.

2'. The composition of claim 1 in which the polymer has about to 97% byweight natural pale crepe rubber and about 3 to 10% by weight of thepolydiene polymer.

3. The composition of claim 2 in which the polydiene is polybutadiene. 1

References Cited UNITED STATES PATENTS 2,551,641 5/1951 Seger et a1.252-59X 3,089,832 5/1963 Black et al. 25259X 3,344,067 9/ 1967 Brannenet a1. 25252X 3,462,249 8/1969 Tunkel 4462 PATRICK P. GARVIN, PrimaryExaminer W. J. SHINE, Assistant Examiner US. Cl. X.R.

